A lung nodule found on a CT scan is almost never cancer — but it deserves expert assessment, not months of anxious waiting. This guide explains exactly what a lung nodule is, what determines whether it is concerning, and what your options are.
Last reviewed: April 2026 · Dr Lawrence Okiror FRCS(CTh) FRCSEd(CTh) · GMC 6150382
A lung nodule — sometimes called a pulmonary nodule, a lung shadow, or a spot on the lung — is one of the most common incidental findings in modern medical imaging. It is defined as a roughly round or oval opacity measuring 3cm or less in its longest dimension. Anything larger than 3cm is classified as a lung mass, which carries a meaningfully higher probability of malignancy and warrants more urgent investigation.
Nodules appear on CT scans as white or grey areas against the dark background of normal aerated lung tissue. They vary considerably in their characteristics — some are solid and well-defined, others have a hazy, part-solid or "ground-glass" appearance. These characteristics, alongside size, location, and clinical history, all contribute to the assessment of how likely a nodule is to be significant.
The critical point — and the one that causes the most anxiety — is that a CT scan cannot reliably tell the difference between a benign nodule and an early lung cancer on appearance alone. That is why expert clinical assessment matters, and why the appropriate response to a lung nodule is neither panic nor dismissal.
The majority of lung nodules are caused by the body's response to a previous infection or irritant — and have nothing to do with cancer. The most common benign causes include:
Granulomas — the most common cause of benign nodules. A granuloma is a small cluster of immune cells that forms in response to infection, most commonly from organisms such as Mycobacterium tuberculosis (TB) or certain fungi including Histoplasma and Aspergillus. Many people carry granulomas without ever having had a symptomatic infection. Once the immune response has resolved, the granuloma may calcify — calcified nodules are almost always benign and can usually be confirmed as such on imaging alone.
Hamartomas — the second most common benign lung nodule, hamartomas are non-cancerous tumours composed of normal lung tissue elements (cartilage, fat, connective tissue) arranged abnormally. They are entirely benign and grow very slowly. On CT, their characteristic appearance — including fat or "popcorn" calcification — often allows confident diagnosis without biopsy.
Scar tissue — previous lung infections, including pneumonia or pleuritis, can leave areas of scar tissue that appear as nodules on CT. These are entirely benign and stable over time.
Intrapulmonary lymph nodes — small lymph nodes that sit within the lung tissue itself, appearing as nodules on CT. These are benign and require no treatment.
Early lung cancer — a minority of lung nodules represent primary lung cancer at an early, operable stage. Less commonly, a nodule may represent a metastasis from a cancer arising elsewhere in the body.
15%
People in lung cancer screening found to have nodules
~1%
Screened individuals ultimately diagnosed with lung cancer
75%+
Screen-detected lung cancers found at early Stage I or II
Lung nodules are extremely common. Studies suggest that up to 50% of adults who have a CT scan of the chest for any reason will have at least one pulmonary nodule identified. In the context of the NHS Lung Cancer Screening Programme — which uses low-dose CT scanning to screen current and former smokers aged 55 to 74 — around 15 in every 100 people scanned have nodules detected. Five-year implementation data published in Nature Medicine in March 2026 confirms that only around 1 in 100 screened individuals are ultimately diagnosed with lung cancer.
This is not a reason to be complacent. It is, however, important context. When you are told you have a nodule on your scan, the statistical probability that it represents cancer is low. The reason expert assessment matters is not to treat every nodule as a suspected cancer — it is to identify the small number that genuinely warrant further investigation and distinguish them confidently from the large majority that do not.
Size is the single most important determinant of risk — but it is not the only one. British Thoracic Society (BTS) guidelines provide a framework for how nodules of different sizes should be managed, based on their probability of malignancy.
| Nodule size | Risk category | Typical recommended approach |
|---|---|---|
| Under 5mm | Very low risk | No further investigation typically needed in low-risk individuals |
| 5–6mm | Low risk | Single follow-up CT at 12 months; discharge if stable |
| 6–8mm | Intermediate | Follow-up CT at 3 months; further assessment if growth or suspicious features |
| Over 8mm | Higher risk | MDT discussion; PET-CT scan; consider biopsy or surgical resection |
| Over 30mm | Lung mass | Urgent investigation — malignancy must be excluded |
These thresholds are a guide, not a rigid protocol. A 7mm nodule with spiculated (spiky) edges and a smoking history warrants more concern than a 9mm smooth, calcified nodule in a non-smoker. Size is assessed in the context of the full clinical picture — which is precisely why a written radiology report, however thorough, is not the same as expert specialist review of the images themselves.
Several factors independently increase the probability that a lung nodule is malignant. None of them in isolation means a nodule is cancer — but their combination influences how urgently and intensively a nodule needs to be investigated.
Smoking history — the most significant individual risk factor for lung cancer. Current smokers and former smokers (defined as having smoked at least 100 cigarettes in their lifetime) carry substantially higher lung cancer risk than never-smokers. The risk persists for decades after stopping, though it diminishes progressively over time.
Age — lung cancer is rare under 40 and its incidence rises sharply with age. The NHS screening programme targets those aged 55 to 74 precisely because this is the age group in which screen-detected cancers are most likely to be found at an early, curable stage.
Family history — first-degree relatives with lung cancer independently increase individual risk, even in never-smokers.
Occupational and environmental exposure — asbestos, radon, silica, arsenic, and certain industrial chemicals are established lung carcinogens. Radon is the second leading cause of lung cancer in the UK after smoking.
Previous cancer history — individuals with a prior cancer diagnosis, particularly cancers with a propensity to metastasise to the lung (colorectal, breast, renal, melanoma, sarcoma), have a higher probability that a lung nodule represents a metastasis.
Spiculated or irregular margins — nodules with a spiky or irregular border carry significantly higher malignancy risk than smooth, well-defined nodules.
Ground-glass opacity (GGO) — a hazy, semi-transparent appearance rather than a solid white density. Pure ground-glass nodules are often slow-growing but can represent early adenocarcinoma. Part-solid nodules — with both a ground-glass component and a solid core — carry higher risk than pure ground-glass nodules.
Upper lobe location — nodules in the upper lobes carry a higher probability of malignancy than those in the lower lobes, reflecting where tobacco-related cancers most commonly arise.
Growth on a previous scan — demonstrable growth between scans is the most significant indicator that a nodule warrants active investigation rather than continued surveillance. A nodule that doubles in volume over a period consistent with lung cancer doubling times (typically 30–400 days) should not be watched further.
Absence of calcification — calcified nodules, particularly those with dense central, laminated, or "popcorn" calcification, are almost invariably benign. The absence of calcification does not indicate malignancy, but its presence is reassuring.
The NHS surveillance pathway for intermediate-risk nodules typically involves repeat CT scans at three, six, and twelve-month intervals. For the majority of patients whose nodules are ultimately benign, this is entirely appropriate — and reassuring once completed. But for those whose nodules are genuinely concerning, the interval between scans can represent a period of preventable delay. The modern question is not whether to watch — it is whether we have better tools to get an answer sooner. In many cases, we do.
The rationale for CT surveillance is sound: most nodules are benign, and the risks of invasive investigation are not trivial. Watchful waiting avoids unnecessary procedures for the majority. But surveillance has a well-documented problem — the interval between scans, which can stretch to months, is psychologically extremely difficult for many patients. Living with an unresolved question about whether you have cancer is not a neutral experience.
Beyond the psychological dimension, surveillance pathways have a clinical limitation: they establish stability or growth retrospectively. By the time growth confirms malignancy, weeks or months have elapsed. For a small proportion of patients — those with fast-growing cancers — this delay can matter.
Modern diagnostic tools have changed this equation for selected patients. Where a nodule warrants tissue diagnosis — because of its size, characteristics, or the patient's risk profile — ION robotic bronchoscopy can now reach and biopsy nodules that were previously inaccessible without surgery, often as a day case. For an intermediate-risk nodule, this can replace three rounds of CT surveillance with a single definitive answer.
Assessment of a lung nodule involves three layers: imaging review, clinical risk stratification, and — where indicated — tissue diagnosis.
The CT scan is the starting point. A specialist thoracic radiologist or thoracic surgeon reviews the images — not just the report — assessing size, morphology, density, location, and any changes from previous imaging. At a first consultation, Dr Okiror reviews CT scan images personally, alongside the written report, to form an independent assessment. The images contain more information than the report alone.
For nodules over 8mm that remain indeterminate after CT review, a PET-CT scan (positron emission tomography combined with CT) can add important information. PET-CT measures metabolic activity — cancerous cells typically show higher glucose uptake than benign tissue, appearing as "hot spots" on the scan. PET-CT is not infallible — small nodules under 8mm and slow-growing ground-glass lesions may be PET-negative even if malignant — but it provides useful additional data for larger, solid nodules.
At Guy's and St Thomas' NHS Foundation Trust, all cases with indeterminate or suspicious nodules are discussed at a specialist multidisciplinary team (MDT) meeting involving thoracic surgeons, thoracic radiologists, oncologists, and respiratory physicians. This collective decision-making process — drawing on the full range of clinical expertise — is the standard of care for any nodule where the appropriate next step is not immediately clear. Private referrals through London Bridge Hospital can access this same level of institutional expertise.
A biopsy provides a tissue diagnosis — the only way to know with certainty whether a nodule is benign or malignant. Not every nodule needs a biopsy. Small, low-risk nodules that are stable on surveillance do not. Clearly benign nodules — calcified, with classic hamartoma features — do not. But for intermediate or high-risk nodules that cannot be confidently diagnosed on imaging alone, a tissue sample may be the most clinically appropriate next step.
There are three main approaches to lung nodule biopsy, each with different indications, risk profiles, and diagnostic yields.
A needle is passed through the chest wall, guided by CT imaging, to sample the nodule. Effective for peripheral nodules close to the chest wall. The main risk is pneumothorax (lung collapse), which occurs in approximately 20–30% of cases and requires a chest drain in around 5–10%. Not suitable for nodules that are small, centrally located, or in areas where the needle path would cross major blood vessels or emphysematous lung.
A camera passed down the throat into the airways. Standard bronchoscopy can biopsy nodules that are close to the main airways — but the majority of lung nodules sit in the outer lung, beyond where a standard camera can reach. EBUS (endobronchial ultrasound) is a related technique used specifically to sample lymph nodes and central nodules, and is an important complementary tool in lung cancer staging but is not designed for peripheral nodule biopsy.
ION is a robotic navigation system that uses a shape-sensing, ultra-thin flexible catheter to navigate through the airways — guided by a pre-procedural CT roadmap and confirmed by real-time cone-beam CT imaging — to reach nodules in the peripheral lung. It is designed specifically for the nodules that standard bronchoscopy cannot reach. A pathologist confirms the sample is adequate while the patient is still in the procedure room, reducing the likelihood of an inconclusive result.
London Bridge Hospital was the first private hospital in Europe to introduce ION bronchoscopy in routine clinical practice outside NHS research trials. The ION service at London Bridge Hospital involves a team of thoracic surgeons and a respiratory physician. At Guy's and St Thomas', the ION service has been operational since April 2025, building on the preceding Medtronic electromagnetic navigation bronchoscopy service — which has now been superseded by ION's superior accuracy and cone-beam CT confirmation. The GSTT programme has carried out over 900 navigational bronchoscopy procedures, with diagnostic yields of 76–89% across a range of nodule sizes and a pneumothorax rate of approximately 2%.
Dr Okiror has made the ION bronchoscopy pathway actively accessible to private patients through London Bridge Hospital — with first consultations typically available within 2–3 days. For many patients with intermediate-risk nodules, ION offers a definitive tissue answer in a single day-case procedure, replacing months of surveillance uncertainty.
The majority of patients with a lung nodule do not need surgery. Surgery is indicated in two main situations: where a biopsy has confirmed lung cancer and surgery offers the best chance of cure; or where a nodule has features that make malignancy sufficiently likely that surgical resection is both diagnostic and therapeutic — removing the nodule and treating any cancer in a single operation.
When surgery is needed, the choice of operation matters. The standard operation for early-stage lung cancer has historically been a lobectomy — removal of the entire lobe of the lung containing the tumour. For most of the last century, this was the operation associated with the best cancer outcomes.
Two major international trials — JCOG0802 and CALGB 140503 — have now confirmed that for small, early-stage tumours (typically under 2cm), a segmentectomy — removal of only the anatomical segment of the lung containing the tumour — achieves equivalent cancer control to a lobectomy while preserving significantly more healthy lung tissue. This means less breathlessness, better exercise capacity, and faster recovery. For patients with emphysema, COPD, or reduced lung reserve, a segmentectomy may make surgery possible when a lobectomy would not be safe.
Robotic surgery enables the precision that makes segmentectomy reliably reproducible. At Guy's and St Thomas', 57.8% of lung cancer operations were performed robotically in 2023–24 — more than double the national average of 24% — with an operative survival rate of 99.16% against a national benchmark of 98.5%. The GSTT programme performed 837 lung cancer resections in 2023–24, and only 6% were wedge resections (the least precise operation) compared to 14% nationally — reflecting a deliberate commitment to anatomically precise, lung-sparing surgery.
Where ION bronchoscopy is used to biopsy a nodule, a small fluorescent dye marker can be placed at the exact nodule site during the same procedure. If surgery is subsequently needed, the da Vinci robotic system's infrared camera detects that marker, allowing the resection to be guided precisely to the nodule — enabling a segmentectomy rather than a lobectomy in many cases. This integrated diagnostic and surgical pathway, available privately at London Bridge Hospital, means that patients move from uncertainty to definitive treatment as efficiently as possible, with the smallest operation appropriate for their situation.
If you have been told you have a lung nodule and want expert assessment without delay, private consultation is available at London Bridge Hospital (SE1) and The Lister Hospital Chelsea (SW1). No GP referral is required. Most new patients are seen within 2–3 days of contacting the practice.
At a first consultation, your CT scan images are reviewed personally and in full — not just the written report. A clear plan is agreed at that appointment. You will not leave without knowing exactly what the next step is, whether that is reassurance, a surveillance scan, or further investigation.
The private pathway draws on the clinical infrastructure of Guy's and St Thomas' NHS Foundation Trust — the UK's largest thoracic surgical programme, and one with outcome data that consistently exceeds the national benchmark across operative survival, resection rates, and minimally invasive surgery adoption.
What is a lung nodule?
A lung nodule is a small, rounded area of tissue — typically less than 3cm in diameter — that appears as a white spot on a CT scan. The vast majority are entirely benign. Only a small minority represent early-stage lung cancer.
Does a lung nodule mean I have cancer?
Almost certainly not. Around 15 in every 100 people who have a CT scan through the NHS Lung Cancer Screening Programme are found to have lung nodules — and the vast majority are benign. Only around 1 in 100 people screened are ultimately diagnosed with lung cancer. That said, every nodule deserves expert assessment rather than assumption.
What size lung nodule is concerning?
Nodules under 6mm are generally very low risk. Nodules between 6mm and 8mm warrant a repeat CT at 3 months. Nodules over 8mm — particularly those with irregular edges, ground-glass appearance, or demonstrable growth — require more urgent specialist assessment, which may include a biopsy. These thresholds are a guide, not a rigid protocol — the full clinical picture always matters.
Do I need surgery for a lung nodule?
Most patients with a lung nodule do not need surgery. The majority are reassured after expert assessment. Where a biopsy is needed, ION robotic bronchoscopy can often provide a tissue diagnosis as a day case without any surgical incisions. Surgery is reserved for confirmed cancer or very high-probability nodules where surgical removal is both diagnostic and therapeutic.
What is the difference between a lung nodule and a lung mass?
A lung nodule is 3cm or less in diameter. Anything larger is classified as a lung mass, which carries a significantly higher probability of malignancy and requires urgent investigation.
What is ION bronchoscopy and how does it help?
ION bronchoscopy is a robotic navigation system that guides an ultra-thin catheter through the airways to reach and biopsy nodules deep in the outer lung — areas previously inaccessible without surgery. A cone-beam CT confirms the exact position before any sample is taken. London Bridge Hospital was the first private hospital in Europe to introduce ION in routine clinical practice, and the pathway is actively accessible to private patients within days.
How quickly can I be seen privately for a lung nodule in London?
New private patients are typically seen within 2–3 days. No GP referral is required. Contact Grace Jones on 020 7952 2882 or pa@lungsurgeon.co.uk. Consultations are available at London Bridge Hospital (SE1) and Lister Hospital Chelsea (SW1).
What happens at a first consultation for a lung nodule?
Dr Okiror reviews your CT scan images personally — not just the written report. The size, shape, density, position, and clinical context of the nodule are assessed together. In most cases, a clear plan is agreed at the first appointment: reassurance and discharge, a surveillance scan, or further investigation. You will not leave without knowing exactly what happens next.
What is a segmentectomy and is it as effective as removing the whole lobe?
A segmentectomy removes one anatomical segment of the lung rather than an entire lobe. For small, early-stage tumours, two major international trials (JCOG0802 and CALGB 140503) have confirmed it achieves equivalent cancer control to a full lobectomy while preserving significantly more healthy lung tissue — meaning less breathlessness, better exercise capacity, and faster recovery. At GSTT, robotic surgery enables this precision operation to be performed routinely.
No GP referral required. Dr Okiror reviews your scan personally at your first appointment and gives you a clear plan — not a further wait.
Request a consultation →Sources and references
British Thoracic Society Guidelines for the investigation and management of pulmonary nodules (BTS, 2015, updated 2023) · Lee et al., Implementation of the NHS England Lung Cancer Screening Programme over 5 years, Nature Medicine, 23 March 2026 · Altorki et al., CALGB 140503 trial, New England Journal of Medicine, 2023 · Saji et al., JCOG0802 trial, The Lancet, 2022 · SCTS National Thoracic Surgery Audit 2023–24 · National Lung Cancer Audit State of the Nation Report 2026 (NATCAN)